CN107227152B

CN107227152B - Near-infrared emission fluorescent carbon dot with up-down conversion function and preparation method thereof

Info

Publication number: CN107227152B
Application number: CN201610178544.6A
Authority: CN
Inventors: 林恒伟; 潘露露; 张凌; 吴潇龙; 马利玲; 冷玉敏; 吴小雪
Original assignee: Ningbo Institute of Material Technology and Engineering of CAS
Current assignee: Ningbo Institute of Material Technology and Engineering of CAS
Priority date: 2016-03-25
Filing date: 2016-03-25
Publication date: 2020-12-11
Anticipated expiration: 2036-03-25
Also published as: CN107227152A

Abstract

The invention discloses a near-red light emitting fluorescent carbon dot with an up-down conversion function and a preparation method thereof. The particle size of the carbon dots is between 1 and 50nm, the positions of generated fluorescence emission peaks are all in the range of more than 670nm and less than or equal to 750nm under the irradiation of exciting light with different wavelengths, and the fluorescence quantum yield is more than 15 percent; the preparation method comprises the following steps: dissolving a carbon precursor into a liquid organic compound to form a mixed reaction solution, heating to form a dark green solution, and washing a solid substance separated from the dark green solution to obtain the carbon dots. The carbon dots have the advantages of up-down conversion near-infrared emission, high fluorescence quantum yield, large Stokes shift with narrow half-peak width, wide application prospect in the fields of fluorescence labeling imaging, drug delivery, disease diagnosis, analysis and detection and the like, simple and rapid preparation process, convenient operation, high yield, no need of complex and expensive equipment, low cost and easy realization of large-scale production.

Description

Near-infrared emission fluorescent carbon dot with up-down conversion function and preparation method thereof

Technical Field

The invention relates to a fluorescent material and a preparation method thereof, in particular to a near-infrared emission fluorescent carbon dot with an up-down conversion function and a preparation method thereof, belonging to the field of chemistry and material science.

Background

In 2006, scientists Sun and the like at the university of claimenson in the united states firstly manufacture a novel carbon nano material, namely carbon quantum dots (carbon dots for short), and as a novel member of a carbon material family, the unique properties and potential applications of the carbon nano material draw more and more attention. Different from the traditional semiconductor fluorescent quantum dots, the carbon dots do not contain heavy metal elements, and the carbon serving as the main component of the carbon dots is one of the main elements forming a living body, so that the carbon dots have lower biotoxicity and better biocompatibility. In addition, the carbon dots also have the characteristics of excitation wavelength dependence, good light stability, up-conversion luminescence and the like, and the near-infrared carbon dots have unique advantages on the basis of retaining the advantages of visible light carbon dots, such as large penetration depth and capability of offsetting interference caused by factors such as light absorption, autofluorescence and the like of biological tissues. The method has a wider application prospect in the fields of chemical sensing and biological imaging, and can be used as a better substitute of semiconductor quantum dots. Although the research on carbon dots has made many important progress in recent years, the optimal fluorescence emission of the obtained carbon dots is mostly concentrated in the visible light region, and the quantum yield of the fluorescence emission of the prepared carbon dots is also low.

Near-infrared fluorescent materials (rare earth luminescent materials, semiconductor quantum dots, organic fluorescent dyes, carbon dots, fluorescent proteins) attract extensive attention of researchers due to the huge application potential of the near-infrared fluorescent materials in the aspects of biological imaging and detection. However, the potential biological toxicity and stability problems exist in a plurality of near infrared fluorescent materials which are reported at present. For example: on one hand, heavy metal leakage and surface organic groups in the near-infrared semiconductor quantum dots may cause cytopathic effect; on the other hand, most of the near-infrared semiconductor quantum dots are synthesized by using metal organic compounds as precursors in organic phases, and toxic organic solvents used in the synthesis process can cause harm to the environment and the health of human bodies, so that the application of the near-infrared semiconductor quantum dots in the aspect of biology is severely limited. Therefore, there is a need to develop a near infrared fluorescent material with better performance.

Disclosure of Invention

In view of the shortcomings of the prior art, the main object of the present invention is to provide a near-infrared emission fluorescent carbon dot with up-down conversion function, which has strong near-infrared red light emission capability, high quantum yield, and up-down conversion fluorescence.

Another object of the present invention is to provide a method for preparing the near-infrared emission fluorescent carbon dot with up-down conversion function, which is simple and fast and has low cost.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

the embodiment of the invention provides a near-infrared emission fluorescent carbon dot with an up-down conversion function, wherein under the irradiation of exciting light with the wavelength of 360-670nm or 700-1100nm, the positions of generated fluorescence emission peaks are all in the range of more than 670nm and less than or equal to 750nm, and the fluorescence quantum yield is more than 15%.

Further, the grain diameter of the carbon dots is between 10 and 50 nm.

The embodiment of the invention provides a method for preparing a near-infrared emission fluorescent carbon dot with an up-down conversion function, which comprises the following steps:

dissolving a carbon precursor in a liquid organic compound to form a mixed reaction solution;

reacting the mixed reaction solution at the temperature of 100-300 ℃ to form a dark green solution or a yellow green solution;

and separating and purifying dark green solid matters in the solution to obtain the near-infrared emission fluorescent carbon dots.

Preferably, the mixed reaction solution contains a carbon precursor at a concentration of 0.1 to 30 wt%.

Further, the carbon precursor is selected from any one of or a combination of two or more of L-reducing glutathione, L-oxidizing glutathione, L-glutathione disodium salt, L-cysteine, D-cysteine, DL-cysteine, D-cysteine hydrochloride-hydrate, L-cysteine hydrochloride-hydrate and N-acetyl-cysteine, but is not limited thereto.

Further, any one, two or more combinations of formamide, N-dimethylformamide, acetamide and N, N-dimethylacetamide are used as the liquid organic compound, but not limited thereto.

Further, the preparation method further comprises the following steps: when the reaction temperature is higher or lower than the boiling point of the liquid organic compound, putting the mixed reaction liquid into a pressurized reactor for full reaction

Preferably, the preparation method further comprises: reacting the mixed reaction liquid for 1-36h at the temperature of 100-140 ℃.

Preferably, the preparation method further comprises: reacting the mixed reaction liquid for 1-18h at the temperature of 140-180 ℃.

Preferably, the preparation method further comprises: reacting the mixed reaction liquid for 1min-12h at the temperature of 180-300 ℃.

For example, in a more specific embodiment, the preparation method may include the following steps:

(1) dissolving a carbon precursor in a liquid organic compound to prepare a mixed reaction solution with a certain concentration;

(2) heating the mixed reaction solution obtained in the step (1) to a certain temperature and preserving heat for a period of time to obtain a dark green solution;

(3) and (3) centrifuging, filtering or dialyzing and separating the dark green solution obtained in the step (2), and washing the obtained precipitate for a plurality of times by using the solution to obtain the near-infrared emission fluorescent carbon dots with the up-down conversion function.

Compared with the prior art, the invention has the advantages that:

(1) the near-infrared emission fluorescent carbon dot (hereinafter referred to as a "carbon dot") with the up-down conversion function has high fluorescence quantum yield (higher than 15%), large Stokes shift, and particularly, the fluorescence emission wavelength of the carbon dot does not change along with the change of the wavelength of the excitation light basically, namely, the fluorescence excited by the light with the wavelengths of 360 plus 670nm and 700nm to 1100nm is near-infrared, so that the carbon dot has wide application prospects in the fields of fluorescence labeling imaging, drug delivery, disease diagnosis, analysis and detection and the like, for example, when the carbon dot is applied to the field of biomedicine, the penetration depth of tissues can be improved, the interference caused by background fluorescence can be avoided, and the imaging resolution can be improved;

(2) the preparation process of the near-infrared emission fluorescent carbon dot is simple and rapid, convenient to operate, high in yield, free of complex and expensive equipment and easy to realize industrial production.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a graph showing a fluorescence spectrum of a carbon dot obtained in example 1 under excitation at 420nm and an emission spectrum at 685 nm;

FIG. 2 is a TEM photograph of the carbon dots obtained in example 1;

FIG. 3 is a two-photon fluorescence spectrum of carbon dots obtained in example 1;

FIG. 4 is a graph showing the fluorescence spectrum of the carbon dots obtained in example 2 under excitation at 420 nm;

FIG. 5 is a graph showing the fluorescence spectrum of the carbon dots obtained in example 3 under excitation at 420 nm;

FIG. 6 is a graph showing the fluorescence spectrum of the carbon dots obtained in example 4 under excitation at 420 nm;

FIG. 7 is a graph showing the fluorescence spectrum of the carbon dots obtained in example 5 under excitation at 420 nm.

FIG. 8 is a graph showing the fluorescence spectrum of the carbon dots obtained in example 6 under excitation at 420 nm.

Detailed Description

The technical solutions in the embodiments of the present invention will be described in detail below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1 glutathione was dissolved in formamide to prepare a solution with a mass fraction of 1%. 50ml of the solution is placed in a 100ml microwave reaction kettle, the reaction kettle is placed in a microwave reactor, and the reaction kettle is taken out after 1 hour of reaction at 160 ℃. And placing the reaction solution in a natural cooling room temperature, adding water to dilute the reaction solution, dialyzing until no fluorescence exists in the dialyzate, and finally obtaining a solid, namely a target product, placing the solid in a vacuum drying oven for drying and then sealing and storing. Elemental analysis tests show that the target product obtained in the example is carbon dots. In addition, the fluorescence emission spectrum and the excitation spectrum of the carbon dot obtained in the present example are shown in fig. 1, the half-peak width of the fluorescence emission peak is narrow, and is only 30nm, the fluorescence emission peak is not substantially changed with the wavelength change of the excitation light, and has a large stokes shift (265 nm). Fig. 1 also shows that the optimum excitation wavelength of the carbon dots obtained in this example is around 405 nm. FIG. 2 is a TEM photograph of the carbon dots obtained in this example. And, the carbon dots obtained in this example were dispersed in water to form a solution, which was red under excitation of a laser with a wavelength of 800nm, and fig. 3 is a two-photon fluorescence spectrum of the carbon dots obtained in this example.

Example 1 glutathione was dissolved in formamide to prepare a solution with a mass fraction of 5%. 50ml of the solution is placed in a 100ml microwave reaction kettle, the reaction kettle is placed in a microwave reactor, and the reaction kettle is taken out after 1 hour of reaction at the temperature of 140 ℃. And placing the reaction solution in a natural cooling room temperature, adding water to dilute the reaction solution, dialyzing until no fluorescence exists in the dialyzate, and finally obtaining a solid, namely a target product, placing the solid in a vacuum drying oven for drying and then sealing and storing. Elemental analysis tests show that the target product obtained in the example is carbon dots. In addition, the fluorescence spectrogram of the carbon dot obtained in the embodiment is shown in fig. 1, and the half-peak width of the fluorescence emission peak is narrow, and the fluorescence emission peak basically does not change with the change of the wavelength of the excitation light, and has a large stokes shift.

Example 2 glutathione was dissolved in formamide to prepare a solution with a mass fraction of 3%. 50ml of the solution is placed in a 100ml microwave reaction kettle, the reaction kettle is placed in a microwave reactor, and the reaction kettle is taken out after 1 hour of reaction at 180 ℃. And placing the reaction solution in a natural cooling room temperature, adding water to dilute the reaction solution, dialyzing until no fluorescence exists in the dialyzate, and finally obtaining a solid, namely a target product, placing the solid in a vacuum drying oven for drying and then sealing and storing. The fluorescence spectrum of the carbon dots obtained in this example is shown in fig. 4, and the half-peak width of the fluorescence emission peak is narrow, and the fluorescence emission peak is not substantially changed with the wavelength of the excitation light, and has a large stokes shift.

Example 3 glutathione was dissolved in formamide to prepare a solution with a mass fraction of 3%. 50ml of the solution is placed in a 100ml microwave reaction kettle, the reaction kettle is placed in a microwave reactor, and the reaction kettle is taken out after 1 hour of reaction at 180 ℃. Placing the reaction solution in a natural cooling room temperature, carrying out centrifugal separation on the reaction solution, washing the obtained precipitate for 4 times by using acetone and methanol respectively, and finally placing the obtained solid, namely the target product in a vacuum drying oven for drying and then sealing and storing. The fluorescence spectrum of the carbon dots obtained in this example is shown in fig. 5, and the half-peak width of the fluorescence emission peak is narrow, and the fluorescence emission peak is not substantially changed with the wavelength of the excitation light, and has a large stokes shift.

Example 4 glutathione was dissolved in formamide to prepare a solution with a mass fraction of 1%. 15ml of the solution is taken and placed in a 20ml high-pressure reaction kettle, then the reaction kettle is placed in an oven which is heated to 160 ℃, and the reaction kettle is taken out after heat preservation is carried out for 6 hours. And placing the reaction solution in a natural cooling room temperature, adding water to dilute the reaction solution, dialyzing until no fluorescence exists in the dialyzate, and finally obtaining a solid, namely a target product, placing the solid in a vacuum drying oven for drying and then sealing and storing. The fluorescence spectrum of the carbon dots obtained in this example is shown in fig. 6, and the half-peak width of the fluorescence emission peak is narrow, and the fluorescence emission peak is not substantially changed with the wavelength of the excitation light, and has a large stokes shift.

Example 5N-acetyl-L-cysteine was dissolved in formamide to make a 1% solution by mass. 50ml of the solution is placed in a 100ml microwave reaction kettle, the reaction kettle is placed in a microwave reactor, and the reaction kettle is taken out after 1 hour of reaction at 160 ℃. And (3) adding water to dilute the reaction solution, dialyzing until no fluorescence exists in the dialyzate, and finally putting the obtained solid, namely the target product, in a vacuum drying oven for drying and then sealing for storage. The fluorescence spectrum of the carbon dots obtained in this example is shown in fig. 7, and the half-peak width of the fluorescence emission peak is narrow, and the fluorescence emission peak is not substantially changed with the wavelength of the excitation light, and has a large stokes shift.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The foregoing is directed to embodiments of the present invention, and it is understood that various modifications and improvements can be made by those skilled in the art without departing from the spirit of the invention.

Claims

1. A preparation method of a near-infrared emission fluorescent carbon dot is characterized by comprising the following preparation steps: dissolving glutathione in formamide to prepare a solution with the mass fraction of 3%; putting 50ml of the solution into a 100ml microwave reaction kettle, putting the reaction kettle into a microwave reactor, reacting for 1 hour at 180 ℃, taking out the reaction kettle, naturally cooling to room temperature, adding water into the reaction solution for diluting, dialyzing until no fluorescence exists in the dialyzate, and finally putting the obtained solid, namely the target product, into a vacuum drying oven for drying and sealing for storage.

2. A preparation method of a near-infrared emission fluorescent carbon dot is characterized by comprising the following preparation steps: dissolving glutathione in formamide to prepare a solution with the mass fraction of 3%; putting 50ml of the solution into a 100ml microwave reaction kettle, putting the reaction kettle into a microwave reactor, reacting for 1 hour at 180 ℃, taking out the reaction kettle, naturally cooling to room temperature, centrifugally separating reaction liquid, washing obtained precipitates for 4 times by using acetone and methanol respectively, and finally drying the obtained solid, namely the target product, in a vacuum drying oven, and sealing and storing.

3. A preparation method of a near-infrared emission fluorescent carbon dot is characterized by comprising the following preparation steps: dissolving glutathione in formamide to prepare a solution with the mass fraction of 1%; placing 15ml of the solution into a 20ml high-pressure reaction kettle, placing the reaction kettle into an oven heated to 160 ℃, preserving heat for 6 hours, taking out the reaction kettle, placing the reaction kettle into a natural cooling room temperature, adding water into the reaction solution for dilution, dialyzing until no fluorescence exists in the dialyzate, placing the obtained solid, namely the target product, into a vacuum drying oven for drying, and sealing for storage.

4. A preparation method of a near-infrared emission fluorescent carbon dot is characterized by comprising the following preparation steps: dissolving N-acetyl-L cysteine in formamide to prepare a solution with the mass fraction of 1%; putting 50ml of the solution into a 100ml microwave reaction kettle, putting the reaction kettle into a microwave reactor, reacting for 1 hour at 160 ℃, taking out the reaction kettle, adding water into the reaction solution for diluting, dialyzing until no fluorescence exists in the dialyzate, and finally, putting the obtained solid, namely the target product, into a vacuum drying oven for drying and sealing for storage.